1. Field of the Invention
The present invention pertains to a method and apparatus for controlling and eliminating the deposition and buildup of paraffin and asphaltene deposits on the inside of downhole oil string lines. More particularly, the present invention relates to the use of an insulating rod having low conductivity interposed between the polish rod and the steel sucker rods of an oil well pumping device.
2. Description of the Prior Art
Paraffin and paraffin clogging from deposits in crude oil has long been recognized as a problem in both pumping crude oil from the ground through the downhole oil string and in the transmission of crude oil through oil pipelines. A variety of mechanical, chemical, electrical heating and magnetic systems have been proposed in the prior art for removing paraffin or reducing the affinity of paraffin to deposit or combine with other well effluent so as to result in paraffin clogging of crude oil conduits which as known by those skilled in the oil industry results in significant down time and problem in removing the plugging or clogging of downhole oil strings and above ground flow lines.
The prior art chemical system for removing paraffin plugging of crude oil transmission lines are costly not only in term of the amount of chemicals required to treat downhole oil strings and flow lines. Typical chemical treatments for each oil well range from $150.00 to $600.00 per month per well.
As a result an effective mechanical system for removing or preventing paraffin clogging has been sought in view of cost effectiveness. Unfortunately, many of the prior art mechanical system have not been effective in removing or preventing paraffin clogging or have required an unpractical number of units be placed in the off transmission line, for example, every five to seventy five feet, which make such systems unfeasible in view of cost and the number of units required and in view of space limitations in downhole oil strings which generally have outside diameters of 3 to 4 inches (7.6 to 10.2 cm) and may be as long as 25,000 feet. Other prior art electromechanical systems, which involve heating, are expensive to operate and maintain which has resulted in the predominant use of chemicals and hot oils and solvents.
Typically some of the prior art de-clogging systems employ hot oil, hot water or chemical solvents that are pumped through tubing into the wellbore to either melt or dissolve the paraffin clogs and thus remove accumulations of paraffin, salt and paraffin scale deposits on the inside of the crude oil line from which the crude oil flows. These prior art system result in substantial down time and costs in terms of heating a sufficient amount of water or oil necessary to melt and dissolve paraffin clogged fines as a result of their length and surrounding environmental conditions of the downhole oil line or the surface or buried oil flow transmission lines. Representative of prior art providing for a paraffin removal with the introduction of hot oil or other solvent for the removal of paraffin from clogged lines is U.S. Pat. No. 3,085,629. Consequently, in recent years, chemicals have been preferred in view of their effectiveness.
Chemical or solvent system while effective and widely utilized in the industry are nevertheless costly. As a result a number of other mechanical, electrical and magnetic systems have been proposed for the removal or reduction of the amount of paraffin deposits resulting from the transmission of crude oil. The most pertinent prior art system known pertaining to preventing the buildup of paraffin by attempting to control electrostatic forces by the insulation of the pump and tubing from the well casing and the ground, attributes paraffin accumulates in oil wells as a result of the actions of electric currents resulting from friction between the moving parts of the well pumping machinery. In U.S. Pat. No. 2,368,777 the friction problem is solved by insulating ground with non conductive washers at such points and in such a manner as to prevent the flow of electric current between the parts and the earth. As such various insulation sleeves and washers are provided between the pumping apparatus and the downhole oil string to reduce the effects of friction and the electrostatic forces which are believed to charge particles in the flow line and cause them to deposit on the inside of the crude oil conduit.
U.S. Pat. No. 2,368,777 does not utilize a special coupling in the oil flow line to dissipate and prevent the building up of the electrostatic forces resulting from the flow of crude oil in flow lines or prevent the deposition of paraffin inside above ground flow tines. U.S. Pat. No. 2,368,777 furthermore does not utilize magnets of the combination of materials of different conductivity and magnetivity in accordance with the present invention for the purpose of not only dissipating frictional forces along the section of the pipe but also to magnetically charge the particles of the constituents of crude oil flowing inside the pipe so as to prevent the subsequent deposition of paraffin, salts and paraffin scale deposits further along the downhole oil string or thereafter in the above ground pipeline or flow line.
U.S. Pat. No. 3,222,878 represents the closest prior art uncovered which pertains to the use of magnetic forces for the purposes of controlling the build up of paraffin deposits in above ground flow lines. U.S. Pat. No. 3,222,878 is not applicable to downhole oil lines in view of the size and arrangement of magnets. This patent appears relevant at first glance but is not particularly relevant to the present invention since U.S. Pat. No. 3,222,878 does not electrically isolate sections of pipe either along the downhole oil string or in surface or subsurface oil transmission flow lines and does not disclose a practical system in terms of practicability or in terms of economic feasibility.
U.S. Pat. No. 3,222,878 does not pertain to a downhole device for oil string lines but pertains only to a device for above ground oil flow lines to prevent the deposition of paraffin and diamagnetic deposits including scale since the arrangement of magnets having a radius of 4{fraction (5/16)}th of an inch could not be utilized downhole since it would not fit down inside an oil string casing which typically are 2 or 2xc2xd inches (5.1 to 6.4 cm) in diameter. The above ground magnetic system of U.S. Pat. No. 3,222,878 furthermore does not electrostatically isolate sections of pipe and requires magnets disposed along the length of the pipe from about 10 to perhaps 150 times the length of the magnetic field. The length of the magnetic field described in U.S. Pat. No. 3,222,378 is produced from a magnet of about 5{fraction (15/16)}th of an inch (15.08 cm) in length which therefore would require repeating the installation of the arrangement of magnets every 5 to about 75 feet (1.5 to 22.9 meters) along the length of the pipe. Therefore even if such a mechanical system could be employed downhole it would be far in excess of the $150 to $600 a month per well and as a result of these and other problems such system as U.S. Pat. No. 3,222,878 have generally resulted in the industry not accepting magnets and magnetic system for the control of paraffin.
U.S. Pat. No. 5,052,491, issued on Oct. 1, 1991, to Harms et al, describes an oil tool and method for controlling paraffin deposits which employs the use of magnets to control paraffin accumulation. The preferred application employs at least two magnets having a north pole and south pole aligned in opposite directions and held in place in relation to a magnetic outer shield or casing by a non-magnetic restraining ring. The non-magnetic inside liner or non-magnetic section of flow line in combination with the magnetic shield increases the magnetic field which, in combination with the electrostatic differential in the materials in the coupling in the oil line, prevents and controls paraffin and other substances having the potential for clogging and blocking downhole oil strings. It has been found that this method has been successful in certain crude oil applications but has not worked in other applications.
U.S. Pat. No. 2,368,777, issued on Feb. 6, 1945, to E. F. Price, describes that the main reason for paraffin accumulation in wellbores is the presence of the electric current resulting from friction between the moving parts of the well pumping machinery. In order to reduce electric current, this patent describes the use of non-conductive washers at such points and in such a manner as to prevent the flow of electric current between the moving parts and the earth.
It is an object of the present invention to provide a method and apparatus for minimizing paraffin and asphaltene deposits inside downhole tubing strings.
It is another object of the present invention to provide a low thermal conductivity barrier to heat flow so as to minimize heat loss for the purpose of minimizing paraffin and asphaltene deposits.
It is still a further object of the present invention to provide a method and apparatus which is easy to use, relatively inexpensive, and very effective.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.
The present invention is a pump apparatus comprising a pumping unit having a head thereon, a polish rod connected to the head of the pumping unit and extending downwardly therefrom, a tubing string having a stuffing box through which the polish rod extends, a single insulating rod (or multiple insulating rods having a length less than 100 feet) connected to a lower end of the polish rod and extending into the tubing, and a sucker rod affixed to an end of the insulating rod opposite the polish rod. The insulating rod preferably has a thermal conductivity of between 0.0167 to 0.06 BTU/(sq. ft.)(hr)(deg.F)(ft). The sucker rod extends into the tubing.
In particular, in the preferred embodiment of the present invention, the polish rod is a steel rod having a connector at a lower end thereof. The insulating rod has a connector at an upper end thereof. The connector of the polish rod is interconnected to the connector of the insulating rod. In particular, a coupling is used which has an internally threaded area at an upper end thereof and an internally threaded area at a bottom end thereof. The internally threaded area of the upper end is affixed to an externally threaded portion at a bottom end of the polish rod. The internally threaded area of the bottom end of the coupling is affixed to an externally threaded portion at a top end of the insulating rod. The insulating rod includes a fiberglass body having a first steel connector at an upper end thereof and a second steel connector at a bottom end thereof. The fiberglass provides the insulating rod with its low thermal conductivity therethrough.
The steel sucker rod has an externally threaded portion at an upper end thereof. A sucker rod coupling is used which has an upper internally threaded area joined to an externally threaded portion at the bottom of the insulating rod. The sucker rod coupling has a lower internally threaded area which is joined to an externally threaded portion of the sucker rod. The sucker rod is connected to a downhole pump.
The tubing and flow line have has an exposed portion extending outwardly of the surface of the earth. An insulating material is affixed around the exposed portion. This insulating material has a thermal conductivity preferably of between 0.0167 to 0.06 BTU/(sq. ft.)(hr)(deg.F)(ft). In particular, this insulating material is fiberglass material which is wrapped around the exposed portion.
The present invention is also a method of reducing paraffin and asphaltene deposits in a pumping oil well comprising the steps of: (1) forming an oil pumping unit having a polish rod connected to a head of a pump unit, (2) affixing a single insulating rod to a bottom end of the polish rod within an oil string tubing; and (3) attaching a steel sucker rod to the end of the insulating rod opposite the polish rod. The insulating rod is formed of an insulating material preferably having a thermal conductivity of between 0.0167 to 0.06 BTU/(sq. ft.)(hr)(deg.F)(ft). In particular, in the method of the present invention, the insulating rod is formed of a fiberglass body. A first steel connector is affixed to one end of the fiberglass body and a second steel connector is affixed to an opposite end of the fiberglass body. The polish rod and the sucker rod are formed of steel material.